Manufacture of benzoates



Patented Nov. 27, 1928.

S. CALCOTT AND HERBERT W. DAUDT, OF PENNS SIGNORS T E. I. DU PONT DE N EMOULRS & COMPANY, OF

A CORPORATION OF DELAWARE.

GROVE, NEW JERSEY, A8- WILMINGTON, DELAWARE,

MANUFACTURE OF BENZOA'I'ES.'

No Drawing; Application filed September 18, 1924, Serial No. 787,608 Renewed February 27, 1928.

This invention is on the art of manufacture of benzoates, particularly water soluble white benzoates, and has particular application in the manufacture of benzoates of the 6 alkali metals, including ammonium. It relates especially to a process for the removal of discoloration due to certain im urities of unknown composition which, in t emselves, cannot be entirely removed by treatment w1th 10 activated carbon. The difficulty is, apparently, inherent in the crude benzoic acid used for making the benzoates, for example, the crude benzoic acid made from phthalic acid by the process disclosed by H. W. Daudt, one of the 5 present applicants, in his U. S. Patent No.

1,551,373, August 25,1925, on process'of making benzoic acid. We have devised a process whereby it is possible to eliminate the dlS- coloration mentioned when using crude benzoic acid, wherefore there is avoided the necesity of, using costl sublimed benzoic acid, While yet obtaining benzoates of satisfactory color. It is the principal object of the present invention to provide such a process.

We have discovered that the products of oxidation, by alkali permanganates, of the aforesaid impurities can be removed by treatment with carbon, preferably activated carbon, and our process is basedu on this discovery. In accordance with t e invention the general procedure may be as follows, it

being understood thatthe procedure givenis but illustrative, the invention not being confined to the details of the example To 2000 pounds of a 10-20% aqueous solution of alkali benzoate, which has been prepared by the neutralization of crude benzoic acid, for example, that made from phthalic acid as above mentioned, add sufiicient alkali 4o permanganate to impart a red color to the solution. Maintain a temperature of '80 to 95 C. for 5 to 15 minutes. Next add 5 to 10 pounds of activated carbon and continue the heating at the stated temperature for 15 to I 30 minutes. Adjust the alkalinity if necessary, with additional benzoic acid, to bring the solution to practically exact neutrality. Filter'at the same temperature; and evaporate and d in the usual manner.

of sodium benzoate,. there may be used, for 1000 pounds of a 10% sodium benzoate solu- As speci cally applied to the production tion, a solution of 2 pounds of potassium permanganate dissolved in 50 pounds of water; the heating with the permanganate may be for 15 minutes at 80 to 95 0.; there may be added 5 pounds of activated carbon and the continued heating may be at said temperature for 30 minutes.

Although it may at times be possible to omit the activated carbon treatment, the use of it affords a better product and allows the use of a slight excess of permanganate, the latter step in turn giving a better product.

We claim: 4

1. The method of manufacturing undiscolored water soluble white benzoates from crude benzoic acid made from phthalic acid which includes heating an aqueous solution of the benzoate with sufficient alkali metal permanganate to oxidize im urities.

The method of manu acturing undis coloredwater soluble white benzoates from crude benzoic acid made from phthalic acid which includes heating an aqueous solution of the benzoate withsuflicient alkali metal permanganate to oxidize impurities, adding carbon to the solution, and continuing the heating in the presence thereof.

3. The method of manufacturing undiscolored water soluble white benzoates from crude benzoic acid made from phthalic acid which includes heating an aqueous solution of the benzoate with suflicient alkali metal permanganate to oxidize impurities, adding activated carbon to the solution, and continuing the heating in the presence thereof.

4. The method of procuring undiscolored alkali metal benzoate from alkali metal benzoate which-has been prepared by the neutralization of benzoic acid made from hthalic acid which method com rises ad ing to substantially 2000 pounds 0 an aqueous solution of the so-prepared benzoate suflicient alkali metal permanganate to impart a red color to the solution, mantaining a tem erature of 80 to 95 C. for 5 to 15 minutes, a ding 5 to 10 pounds of activated carbon and contmuing the heating at said temperature for 15 to 30 minutes, filtering, and isolating the benzoate.

5. The method of procuring undiscolored sodium benzoate from sodium benzoate which has been prepared by the neutralization of 2 means? benzoic acid made from phthalic acid which pounds of activated carbon and continuing method Comprises adding to substantially the heating at said temperature for 30 min- 1000 pounds of a 10%-20% aqueous soluutes, filtering, and isolating the benzoate. 10

tion of the so-prepared benzoate, a solution In testimony whereof We affix our signa- 5 of 2 pounds of potassium permanganate in tures.

50 pounds of Water, maintaining a tempera- WILLIAM S. CALGUTT.

cure of 85 t0 95 C. for lfiminutes, adding 5 HERBERT W. DAUDT. 

